<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
        <meta http-equiv="X-UA-Compatible" content="ie=edge"/>
        <title>Document</title>
        <style>
            div{width: 100px; height: 100px; background-color: red; margin: 50px}
        </style>
        <script>
            window.onload = function(){
                var aDivs = document.getElementsByTagName("div");
                aDivs[0].onclick = function(){
                    //宽变成300
                    startMove(this, "width", 300);
                }

                aDivs[1].onclick = function(){
                    //高变成300
                    startMove(this, "height", 300);
                }

                aDivs[2].onclick = function(){
                    //marginLeft => 300
                    startMove(this, "marginLeft", 300);
                }

                aDivs[3].onclick = function(){
                    //fontSize => 100
                    startMove(this, "fontSize", 100);
                }
            }


            //startMove(oDiv, "width", 300);
            function startMove(node, attr, iTarget){
                clearInterval(node.timer);
                node.timer = setInterval(function(){
                    //计算速度
                    var iCur = parseInt(getStyle(node, attr));
                    var speed = (iTarget - iCur) / 8;
                    speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);

                    if(iCur == iTarget){
                        clearInterval(node.timer);
                    }else{
                        node.style[attr] = iCur + speed + 'px';
                    }
                }, 30);
            }

            //获取当前有效样式浏览器兼容的写法
            function getStyle(node, cssStr){
                return node.currentStyle ? node.currentStyle[cssStr] : getComputedStyle(node)[cssStr];
            }
        </script>
    </head>
    <body>
        <div></div>
        <div></div>
        <div></div>
        <div>div文本</div>
    </body>
</html>